Flexure fatigue tester



Nov. 27, 1962 Q R. A. CRANE ETAL FLEXURE FATIGUE TESTER 2 Sheets-Sheet 1Filed Aug. 24, 1959 ATTORNEY Nov. 27, 1962 R. A. CRANE ETAL 3,065,632

FLEXURE FATIGUE TESTER Filed Aug. 24, 1959 2 Sheets-Sheet 2 If!!! I asiffiigagd M145 Lmkgg United States Patent 3,065,632 FLEXURE FATIGUETESTER Robert A. Crane, Concord, and Prentice C. Wharff, Jr.,

Lafayette, Calif, assignors to The Dow Chemical Company, Midland, Mich,a corporation of Delaware Filed Aug. 24, 195'), Scr. No. 835,794 16(llaims. (Cl. 73-91) This invention relates to fiexure fatigue testersand is particularly directed to an improved apparatus for testing theresistance to fiexure of single filament specimens.

Various factors affect the wear of filaments and the useful life offabrics made of fibers. Among these factors is the effect of tension,compression, and bending of flexing forces on the filaments of which thefabric is made, as well as abrasion of the fibers as by friction,surface cutting, and fiber plucking. Friction and surface cuttingproduce direct damage to the filament at local points of contact withabrasive elements, while fiber plucking and other processes whichproduce fiber strains may cause immediate or dynamic fatigue rupture offilaments in tension, compression, or bending.

Since most fabrics, when in use, undergo considerable folding, creasing,and similar relative bending or twisting of the filaments, it is ofconsiderable importance to be able to determine the resistance ofvarious fibers to bending or flexure stress. In order to be able tocompare test results, it is desirable that the actual stress on thefilament have some definite value. It must be borne in mind that flexureof a filament places substantially one-half of the crosssectional areaundergoing flexure in compression, while the other half of thecross-sectional area is in tension. The degree of compression andtension at the point of flexure is affected both by the angle of thebend at this point and by the stress or tension on the fiber whichextends in both directions from the point of flexure. The first of thesefactors also is alfected by the sharpness or the radius of curvature atthe point of the bend. This latter is readily understandable, as itdirectly affects the compression and tension in the parts of thefilament undergoing flexure. It is desirable, therefore, that the angleat which the filament is flexed, and the radius of curvature of theflexing edge, and the tension in the filament eX- tending away from thepoint of fiexure, all be definitely determined and recorded, or at leastmaintained constant, in connection with tests of the resistance offilaments to fiexure, so that results of such tests may be of value forcomparative purposes.

In certain instances, it may be found that the speed at which theflexure is produced will have an effect upon the resistance of filamentsto rupture under flexure, but this generally can be attributed to heatwhich is developed by the flexure and which is not fully dissipatedduring the test. Such a retention of heat in effect changes the ambient, and, therefore, changes the conditions under which the test isperformed. In some instances, it may be desirable also to record ambienttemperature and humidity, so that a comparison of the results willindicate whether the qualities of the filament undergoing a flexure testare affected by ambient conditions and provide a standard for comparisonof fiexure tests of different filament materials.

In order to provide a flexure fatigue tester for measuring results whichmay provide comparisons to gauge the qualities of difierent filamentsand filament materials, it is desirable that the instrument be capableof flexing a fine filament in a reproducible manner over an accuratelyformed flexing edge of definite radius, recording or registering a largenumber of test cycles for measuring the number of flexures of a specimenfilament prior to rupture thereof, and definitely determining the pointat which it breaks. strument incorporates features which provide all ofthe In carrying out the present invention, the in- ECC aboverequirements and, in particular, provides for flexing or bending afilament by rubbing it back and forth over a substantially roundedflexing edge at an angle of about at the point of flexure. Since singlefibers usually are not capable of supporting a very great weight intension, it is necessary that small weights be utilized to hold thefibers stretched taut over the flexing edge. While various weights maybe used for this purpose, it has been found that small weights, usuallyless than one gram, provide the needed tension in a filament to maintainit stretched continuously and uniformly over the flexing edge withoutimposing undue tensile forces thereon.

When a filament undergoing test ruptures, it generally does so by abreaking at one point, so that the weight depending freely from the endof the filament falls away from the flexing edge. In the presentinvention advantage is taken of this action by providing a switch whichis actuated by the Weight as it falls with the broken filament to stop acounter which is responsive to the number of reciprocations of themechanism which pulls the filament back and forth over the flexing edge.Since the tensioning weights on the filaments are small, a veryimportant part of this invention is the provision of a sensitive lowcontact pressure switch which is adapted to close an electric circuitwhen engaged by the tensioning weight so as to stop the operation of thecounter.

In the illustrated embodiment of this invention, this sensitive lowcontact pressure switch comprises a cup member with a split femaleconical surfacehaving sides which are electrically insulated from eachother and partially coated with an electrically conducting paint. Thiscup switch is placed directly under the tensioning weight on thefilament, so that when the filament breaks the weight falls into the cupand closes an electrical circuit between the split conical conductivesurfaces thereof. This switch is disclosed and claimed in copendingapplication Serial No. 835,793, filed August 24, 1959, of Robert A.Crane and assigned to the same assignee as the present application.

A practical embodiment of this invention can readily be made to includea number of sensitive low contact pressure switches and mounting meansfor supporting a corresponding number of specimen filaments. A separatecounter is provided for each split cup and filament mounting, and allare adapted to be operated simultaneously in response to thereciprocations of the filament mounting member.

Each counter is adapted to be stopped in response to an electricalsignal which is established when its respective filament breaks, and thetension weight thereon .closes the electric circuit through the lowcontact pressure switch. With such a tester, a single filament may betested or a number of individual filaments may be tested simultaneouslyup to the number which can be accommodated by the mounting membercorresponding to the number of low contact pressure switches in theinstrument.

An object of this invention is to provide an improved flexure fatiguetester.

Another object of this invention is to provide a fiex-ure fatigue testerfor simultaneously testing a plurality of individual filaments andrecording the number of flexures of each individual filament withoutstopping the instrument when each filament breaks.

A further object of this invention is to provide an improved flexurefatigue tester capable of testing a plurality of individual filamentsunder flexure and automatically counting the number of flexures of eachindividual filament undergoing test.

Still another object of this invention is to provide an improved flexurefatigue tester in which individual filaments may be stretched over aflexing edge by -a relatively very small tensile force produced by avery light weight and to utilize the light weight to actuate a sensitivelow contact pressure switch for indicating the rupture of its respectiveattached filament.

Further objects and advantages of this invention will become apparentfrom the following description referring to the accompanying drawings,and the features of novelty which characterize this invention will bepointed out with particularity in the claims appended to and forming apart of this specification.

In the drawings:

FIG. 1 is a perspective view of a flexure fatigue tester incorporatingan embodiment of the present invention;

FIG. 2 is a perspective view of a low contact pressure switch of thetype shown in the instrument illustrated in FIG. 1;

FIG. 3 is an elevational view, in half-section, taken along a planeindicated at 33 in FIG. 2, showing details of the low pressure switch;

FIG. 4 is a top plan view of the low contact pressure switch shown inFIGS. 2 and 3;

FIG. 5 is a bottom plan view of the low contact pressure switch shown inFIGS. 2, 3, and 4;

FIG. 6 is a schematic diagram of the major operating parts and circuitcomponents of the flexure fatigue tester shown in FIG. 1, certain partsbeing shown in partial section or broken away to illustrate detailsbetter; and

FIG. 7 is a fragmentary perspective view of an instrument, similar tothat shown in FIGS. 1 and 6, in which the rounded flexing edge is formedby a wire or a rod.

Referring to the drawings, an improved flexure fatigue tester isillustrated which is adapted to test simultaneously a number ofindividual filaments. This invention is equally applicable to filamentflexure fatigue testers for testing a single filament or for testing arelatively large number of filaments simultaneously. Where a singlefilament only is to be tested, the instrument need only be provided witha simple counter which can record or register the number of cycles towhich a filament is subjected vin. flexingiL-over a suitable flexingedge.

In most instances, and particularly for production quality control, itwill be found desirable to construct the instrument so that it cansimultaneously test a plurality of filaments and simultaneouslyindividually record or register the flexing -cycles to which eachindividual filament is subjected.

In the flexure tester illustrated in FIG. 1, ten filaments are adaptedto be tested simultaneously. The instrument may conveniently beassembled in a housing 1 in which all of the principal operating andmeasuring elements are mounted. In this embodiment, a relatively narrowthin flexing bar member 2 is rigidly mounted on three supporting posts 3and secured to the upper ends of these posts by clamping plates 4, withthe flat sides of the flexing bar -member 2 extending upwardly so thatthey are so stantially vertical when the instrument is placed on a levelsupporting surface. The flexing bar member 2 is pro- -vided with acurved flexing edge 2' accurately formed to a uniform curvature andsize, preferably rounded to a diameter between .001 and .005 inch, orabout .5 to 5 filament diameters. Other sizes of flexing edges may beused where relatively large filaments are to be tested, however, inorder to obtain practical tests of single filaments formed of fibersgenerally used in textile manufacture, these relatively small diameterswere found to give test results which bear a significant degree ofcorrelation with the rate of their destruction in fabrics during actualuse.

A plurality of filaments is adapted to be tested simultaneously by beingdrawn back and forth across the flexing bar member 2 by a suitablemounting member. In this embodiment, the mounting member comprises afilament mounting bar 5 provided with a plurality of longitudinallyspaced upwardly extending pegs 5, which are adapted to be engaged byfilament holding tabs 6, secured in any suitable manner, as by adhesive,to the ends of filaments 7. The mounting bar 5 is adapted to besupported by a pair of drawbars 8, an end of each of which is mounted inone end of the filament mounting bar 5. In such a construction, it ishighly desirable that slight misalignment between the drawbars shouldnot bind or otherwise adversely aifect the smooth operation of theinstrument.

The mounting of the drawbars Sin the filament mounting bar 5 canconveniently be utilized to assure an easy selfadjustment of thedrawbars that compensates for any parallel misalignment in the drawbarsand also assures proper positioning of filaments undergoing test. Thiscan be done by mounting an end of one drawbar 8 in a longitudinallyextending slot 9 which bifurcates one end of the mounting bar 5 andmounting a corresponding end of the other drawbar 8 in a closely fittinghole in the other end of the bar 5. This fixes the transverse positionof the filament mounting bar 5, and thus the position of the testfilaments. These drawbars 8 are slidably supported by any suitablebearings, such as journal bearings 10 in hearing blocks 11, mounted onthe sides of the housing 1 adjacent to the upper ends of these sides.This arrangement of the bearing supports for the drawbars 8 maintainsthe drawbars substantially in parallelism and further minimizes thepossibility of binding of the drawbars on the filament mounting bar 5.

Filaments 7 are adapted to be drawn back and forth across the flexingedge 2 of the fiexure bar 2 by reciprocation of the filament mountingbar 5. Preferably this reciprocation of the mounting bar should beperformed at a regular operating cycle speed with a minimum of abruptchanges in speed. This can be conveniently obtained by operating thelnounting bar 5 sinusoidally, so that it gradually approaches standstillat both ends of its travel and gradually accelerates from suchstandstill positions during each part of its operating cycle. Suchsinusoidal reciprocation of the mounting bar 5 can readily be obtainedby an eccentric actuating mechanism which rotates at a substantiallyconstant speed.

In the illustrated embodiment, this eccentric actuating mechanismcomprises a roller drive member 12 rotatably mounted on a drive pin 13mounted on a crankarm 14. This crankarm 14 is driven by an eccentric 15,which is adapted to revolve within an eccentric race 15 in thecr-ankarrn 14, and the eccentric 15 is drivingly mounted on a suitabledrive shaft 16, which is adapted to be driven by any suitable primemover, such as an electric motor 17. Operation of the motor 17 rotatesthe drive shaft 16 and the eccentric 15 within the race 15', so as tocause the crankarrn 14 to oscillate back and forth and to move theroller drive member 12 toward and away from the flexing bar 2. Thefilament mounting bar 5 is adapted to be held in engagement with theroller drive member 12 by the drawbars 8 which are resiliently biasedaway from the mounting bar 5 'by compression springs 18 suitably seatedagainst the rear end of the bearing blocks 11 and spring seat washer 18'mounted on the outer ends of the bars 8, The force of these springs istransmitted to the ends of the filament mounting bar 5 through washers19, which are loosely mounted on the ends of the bars 8 on the sidesthereof away from the bearing blocks 11 and are secured to the ends ofthe drawbars 8 by any suitable means, as cotterpins 20. In this manner,the drawbars 8 resiliently bias the filament mounting bar 5 into firmdriving engagement with the roller drive member 12, so that the mountingbar 5 will reciprocate sinusoidally with the oscillatory movement of theroller member 12, and transmit this sinusoidal reciprocating motion tofilaments 7 mounted on the bar.

In order to maintain the filaments 7 continuously stretched taut overthe flexing edge 2' of the flexing bar 2, the free ends of the filaments7 are secured in any suitable manner, as by adhesive, to holding tabs 6similar to the holding tabs 6, and suitable light weights 21 ofelectrically conductive material and predetermined size are attached tothe holding tabs 6. The weights 21 may be of any suitable form and, ashas been previously stated, preferably are less than one gram, so as tosubject the specimen filament to a minimum tensile stress whilemaintaining it taut in both directions from the flexing edge 2'.

With such an arrangement the filament will be drawn back and forthacross the flexing edge 2' until the bending or flexure fatigue of thefilament will cause it to break. By arranging the flexing edge 2' of theflexing bar member 2 in substantially the same horizontal plane as theupper supporting surface of the mounting bar 5, the filaments 7 arestretched across the flexing edge 2' at substantially a right angle.Since all of the filaments tested in a given instrument of this typewill be bent at substantially the same angle over the flexing edge ofthe flexing bar member and for any given tests the curvature of theflexing edge 2 will be maintained constant, the use of weights 21 of aknown and uniform size provides for readily gauging the flexingqualities of a filament in accordance with the number of flexing cyclesto which a filament is subjected prior to breaking.

In accordance with the present invention, the number of flexing cyclesto which each individual filament is subjected is adapted to be countedWithout requiring that the apparatus be stopped until all of thefilaments undergoing tests have been broken. This can readily be done bycounting the number of times that the mounting bar 5 is reciprocatedfrom the time that the apparatus is put into operation until eachrespective fiber breaks. In order to count the reciprocations of themounting bar 5 a plurality of counters 22, preferably of theelectromagnetic type, corresponding to the number of filament mountingpegs 5 on the mounting bar, is provided. These counters conveniently aremounted on a front panel 23 of the instrument housing to provide foreasy reading thereof. For further convenience, these counters 22 may benumbered, as indicated in FIG. 1, by numbers which correspond to thefiber mounting pegs on the mounting bar.

These counters may be of any conventional type, and each is adapted tobe operated by a solenoid coil 24 suitably connected to a source ofelectrical power supply 25 through the contacts 26" of a relay 26, andcontacts 27 of a mechanically operated circuit breaker 27. The circuitbreaker 27 may be of any suitable type for periodic operation inresponse to operation of the mounting bar 5 so as to open and close theelectrical circuit through its contact 27 in accordance with each cycleof operation of the mounting bar. The illustrated embodiment of thiscircuit breaker 27 shows a cam 28 mounted on the motor drive shaft 16and drivingly rotatable therewith, so as to operate a follower 28'mounted on a circuit breaker operating rod 29. A compression spring 36is arranged between a stationary spring seat 31 and a follower mountingbracket 32 on the end of the operating rod 29* so as resiliently to biasthe follower 28' into engagement with the cam 23. In this manner, everycycle of reciprocation of the mounting bar 5 .produces a correspondingoperation of the circuit breaker 27 to close an electrical circuitthrough the contacts 27 so as to energize the solenoid coils 24- throughtheir respective relay contacts 26' and thus to record .or registeranother cycle of operation.

In order individually to count the number of cycles of flexing of anyindividual filament undergoing test, it is necessary that its respective.counter 22 be deenergized when the filament breaks. In accordance withthe present invention, advantage is taken of the fact that when thefilament 7 breaks its stretching weight 21 will fall away from theflexing bar member 2, and this weight can be utilized to operate aswitch which will deenergize its respective counter solenoid coil 24.Since the stretching weights 21 are purposely made relatively light itis necessary that switches operable by such weights as they fall be of avery low contact pressure type. Such a switch can conveniently take theform of a pair of electrically conductive elements which are insulatedfrom each other and are adapted to beconnected electrically by a weightwhich falls upon the conductive elements when its respective filament isbroken.

In the illustrated embodiment of this invention the pair of electricallyconductive elements of the low contact pressure switch may convenientlybe formed as elements on an integral cup member 33 of suitableinsulating material, such as a plastic. As is more clearly shown inFIGS. 2, 3, and 6 the cup member 33 preferably comprises an innerconcave surface in the form of an inverted frustum of a cone with thebase 34 thereof adapted to face upwardly for the reception of a 'Weight21 when the respectively connected filament 7 breaks. One of these cupswitches is arranged substantially in longitudinal alignment with itsrespective mounting peg 5 and is adapted to be directly under one of theweights 21 attached to a specimen filament secured to its respectivepeg. This arrangement is more clearly shown in FIG. 1. Each cup member33 is divided substantially diametrically thereof by a split 35 so as toseparate the inwardly tapered female conical surface of the invertedfrustum of a cone forming the cup into two substantially equal sections36. The split 35 preferably extends longitudinally of the cup member 33substantially to the apex or small end 34 of the frustum of the coneforming the inner cup surface. The two electrically conductive elementsof the low pressure switch are formed on the two split portions 36 ofthe cup member 33 by simply coating the inner surface of each of thesetwo portions of the cup with any suitable electrical conductivematerial, such as a silver paint. This forms a thin layer 37 ofelectrically conductive material which preferably extends into theinverted conical surface a distance short of the apex of the cone, asindicated by the lower end 37 of the coating.

In order to provide a convenient means for electrically connecting eachof the electrically conductive elements formed by the layers 37, a pairof longitudinally extending passages 38 is drilled or otherwise suitablyformed in the base of the cup member 33, preferably in a plane atsubstantially right angles to the plane of the slot 35. These passages38 extend into the cup any suitable distance and are adapted to receiveelectrical conductors 39 and 39 which are fastened in position in thecup member 33 by set screws 40 which extend into the cup member from theoutside thereof and press against the ends of the conductors 39 and 39'.These set screws 40 form convenient terminals for the .conductors 39 and39 to which the electrically conductive elements 37 can be connected.Such connections between the electrically conductive elements 37 and theset screws 40 can conveniently be made by simply extending theelectrically conductive paint coating over the outer edge of the cupmember 33 and a portion of the outside of the two split halves of thecup member 33, as indicated at 41, to a position where this electricallyconductive coating covers the heads of the set screws 40. Preferably theoutside coating 41 narrows down from the full width of the semicircularend of the cup member 33 to substantially the size of the set screw 40,and care is taken to assure that the paint does not cover the sides ofthe slot 35. In this manner, the two electrically conductive elementsformed by the inner layer 37 and the outer coating or connection 41 areelectrically insulated from each other by the slot 35 and by theinsulating material of which the cup member 33 is made.

The conductors 39 and 39 are respectively connected to the filament 42and grid 43 of an amplifier 44 having a plate 45 forming part of anamplifying circuit for energizing the coil of the relay 26 connected toeach of the counter solenoid coils 24. With this arrangement, the cam 28on the driveshaft 16 energizes the solenoid coil 24 of counter 22through the contacts 27' of the circuit breaker 27 and the relaycontacts 26 of the. relay 26 for each cyclic reciprocation of thefilament mounting bar 5. Thus, all of the counters 22 simultaneouslyrecord or register each cycle of reciprocation of the mounting bar eachtime they are connected to the source of electrical power supply 25. Onbreakage of any of the filaments 7, its respective weight 21 will falland be deposited within the inverted cone forming the upper portion ofthe cup member 33. This should d sconnect the respective counter fromthe energizing circuit through the circuit breaker contacts 27.

In order to assure that each weight will properly close its switchcircuit, each weight 21 preferably is formed of a suitable width, whichmay comprise a transversely extending crossbar portion 21' havingangularly extending ends 21", to enable it to span the space between thetwo electrically conducted elements formed by the layers 37 within thecup so as to electrically connect these two elements. In order to assureagainst the accidental arrangement of the weight 21 within a cup member33 in a manner in which the weight would not span the space between thetwo electrically conducted layers 37, the weight member 21 preferably isformed with a longitudinally extending guide rod portion 47 and the cupmember 33 is formed with a longitudinally extending passage 46 whichextends from the lower end of the member 33 to the apex or small end 34'of the frustum of a cone forming the cup surfaces of the switch. Withthis construction, when a weight 21 falls within a cup member 33, theguide rod portion 47 will fall into the passage 46 and will guide theweight 21 downwardly into the cup member until the crossbar portion 21'thereof contacts the two electrically conductive layers 37. Theangularly extending ends 21 of the crossbar portion 21' should be longerthan the width of the slot 35, so as to prevent the crossbar portion 21'from becoming lodged in the slot 35 and thereby failing electrically toconnect the two electrically conductive element layers 37.

In this manner when a specimen filament breaks, its respective weight 21will fall into a split cup switch member 33 and the crossbar portion 21thereof will be guided into electrical contact with the split femaleconical surface layers 37 thereby electrically connecting these surfacesand completing an electrical circuit from the source of electrical power25 through the amplifying circuit. This supplies a biasing signal to thegrid 43 of the amplifier 44' which closes an electrical circuit throughthe amplifier 44 and energizes the coil of the relay 26. Suchenergization of the coil of the relay 26 operates this relay to open theelectrical circuit through the relay contacts 26' so as to deenergizethe counter solenoid coil 24 which stops the operation of the respectivecounter 22. Obviously, the counter control circuit could be connected sothat the relay 26 would normally be energized, and when a filamentbroke, so that a weight 21 fell into a cup switch 33, the respectivegrid 43 would bias its tube 44 so as to open-circuit the coil of therelay 26. A simple rearrangement of the relay contacts to provide foropening the circuit through the relay contacts when its coil isdeenergized in this alternative control circuit will give the samecounter operation as in the illustrated circuit. In this manner, eachcounter 22 will record or register only the cycles of operation of themounting bar 5 during which its respective weight 21 is held suspendedout of contact with the electrically conductive element layers 37 by itsrespective filament 7. After a filament 7 'has broken and its weight 21has fallen into its switch cup member 33, its counter 22 will remaininoperative as long as the weight 21 remains in the cup member 33. Itthus becomes unnecessary to disconnect manually the various counter ofthe instrument, as they will remain deenergized until the weights 21 aremanually removed from the cup members.

' For convenience, it may be desirable to disconnect a counter from theelectrical circuit to assure that it will not be reconnected by theremoval of its weight member. A suitable manually operable switch 48 maybe electrically connected in the circuit of each counter solenoid coil24 for electrically connecting and disconnecting this coil in circuitwith its respective relay contacts 26'. If desired, a master switch 49also may be provided for electrically connecting and disconnecting theentire electrical system of the instrument from the source of electricalpower supply 25, and an indicator light 50 may be connected across theinstrument side of the terminals of the switch 49 to indicate when theinstrument is connected to the source of electrical power supply. Inthis manner, a single filament or a plurality of filaments may readilybe tested for their resistance to flexure, and comparable results willbe obtained. Also by using weights of different sizes and by changingthe curvature of the flexing edge, different aspects of the flexurecharacteristics can be checked.

Under certain circumstances, it may be found desirable to vary thecurvature of the flexing edge of the flexure fatigue tester in order todetermine the effects on filaments of more or less acute bending orflexure. This may be done by substituting a flexing bar 2 having aflexing edge 2' rounded on a different diameter. FIG. 7 illustrates amodification of the flexing edge member in which the flexing edge isformed by the curved or rounded surface of a relatively smallcylindrical element 51, such as a wire or rod. This small cylindricalelement 51 may conveniently be clamped in suitable grooves 4 and 3formed respectively in the ends of the clamping plates 4 and supportingposts 3. The clamping plates 4 are suitably secured to the post 3, as byscrews 52, to assure holding the small cylindrical element 51 taut andrigid throughout its length between the posts '3. The remainder of theflexure tester illustrated in this figure may conveniently comprise thesame basic and operating elements and circuits as that illustrated anddescribed with reference to FIGS. 1 through 6. This type of flexing edgeelement 51 has the advantage of being more readily replaceable and ofassuring a uniformity to the size of the flexing edge for various tests,as a simple wire of given diameter may be stretched between thesupporting posts 3, and, by recording the size of wire used, the size ofthe flexing edge can be assuredly reproduced, even if the originalflexing edge element should be lost.

While a particular embodiment of this invention has been illustrated anddescribed, modifications of the instrument and various of its mechanicaland electrical components may occur to those skilled in the art. It isto be understood, therefore, that this invention is not to be limited tothe particular details disclosed, and it is intended in the appendedclaims to cover all modificatrons within the spirit and scope of thisinvention.

We claim:

1. A filament flexure fatigue tester comprising a flexing member havinga curved surface forming a flexing edge, means rigidly mounting saidflexing member for maintaining a fixed flexing edge, means including areciprocable filament mounting member and a drive for reciprocating afilament mounted on said mounting member back and forth over saidflexing edge, mean for counting the reciprocations of a filament oversaid flexing edge, a Weight of predetermined size adapted to be attachedto a specimen filament which is secured to said mounting member andwhich extends over said flexing edge, and means for stopplng saidcounting means on breakage of the specimen filament secured to saidmounting member.

2. A filament flexure fatigue tester comprising a flexng bar memberhaving a curved surface forming a flexing edge, means rigidly mountingsaid flexing member for maintaining a fixed flexing edge, meansincluding a filament mounting bar having a plurality of longitudinallyspaced upwardly extending pegs for mounting filament holding tabsthereon, means including a pair of drawbars arranged with one end ofeach operatively engaging a separate end of said mounting bar forsupporting said mounting bar, bearing means for slid'ably supportingsaid drawbars substantially in parallelism, means for resilientlybiasing each of said drawbars in a direction away from said mounting barand thereby resiliently drawing said drawbar ends into operativeengagement with said mount ing bar, means operatively engaging saidmounting bar and cooperating with said drawbars for reciprocating saidmounting bar towards and away from said flexing edge, a plurality ofelectrical means for counting the reciprocations of said mounting bar, aplurality of weights each of predetermined size adapted to be attachedto a specimen filament which is secured to one of said mounting pegs andwhich extends over said flexing edge, and means comprising an electricalcontrol circuit connected to each electrical counting means fordeenergizing each respective counting means on breakage of the specimenfilament secured to its respective mounting peg.

3. A filament flexure fatigue tester comprising a flexing bar memberhaving a curved surface forming a flexing edge, means rigidly mountingsaid flexing member for maintaining a fixed flexing edge, meansincluding a mounting member for concurrently mounting a plurality offilaments thereon and a drive therefor sinusoidally reciprocating saidmounting member for reciprocating a filament mounted thereon back andforth over said flexing edge, a plurality of electrical means forcounting the reciprocations of said mounting member each arranged forassociation with one of said filament mountings, a separate electricallyconductive Weight of predetermined size adapted to be attached to eachspecimen filament which is secured to said mounting member and whichextends over said flexing edge, means comprising an electrical controlcircuit connected to all of said electrical counting means fordeenergizing each respective counting means on breakage of the specimenfilament secured to said mounting member on the mounting respectivelyassociated with said counting means, said electrical control circutincluding a separate circuit breaker connected to each of said countingmeans for controlling the energization thereof. and means including aseparate low contact pressure switch for energizing each respectivecircuit breaker responsive to breakage of the specimen filament associated therewith whereby said circuit breaker is actuated to open circuitposition and said counting means is deenergized, said low contactpressure switch comprising a pair of electrically conductive elementsinsulated from each other and adapted to be electrically connected bysaid weight on breakage of said specimen filament and thereby toenergize said circuit breaker.

4. A filament fiexure fatigue tester comprising a flexing bar memberhaving a curved surface forming flexing edge formed to a uniformcurvature and size, means including a filament mounting member and adrive sinusoidally reciprocating said mounting member for reciprocatinga filament mounted thereon back and forth over said flexing edge,electrical means for counting the reciprocations of said mountingmember, an electrically conductive weight of predetermined size adaptedto be attached to a specimen filament which is secured to said mountingmember and which extends over said flexing edge, means comprising anelectrical control circuit connected to said electrical counting meansfor deenergizing said counting means on breakage of the specimenfilament secured to said mounting member, said electrical controlcircuit including a circuit breaker connected to said counting means forcontrolling the energization thereof, a signal amplifying circuit forenergizing said circuit breaker to open circuit position whereby saidcounting means is deenergized, means including a low contact pressureswitch for supplying a biasing signal to said signal amplifying circuitresponsive to breakage of said specimen filament, said low contactpressure switch comprising a pair of electrically conductive elementsinsulated from each other and adapted to be electrically connected bysaid weight on breakage of said specimen filament and to said amplifyingcircuit for supplying said biasing signal thereto.

5. A filament exure fatigue tester comprising a flexing member, meansincluding a filament mounting bar for mounting a plurality of filamentholding tabs thereon, said mounting bar having a slot bifurcating an endthereof, means including a pair of drawbars arranged with one end of oneof said drawbars loosely extending through said mounting bar slot forsupporting said mounting bar and having means on the end of said onedrawbar for operatively engaging the respective adjacent end of saidmounting bar and the corresponding end of the other of said drawbarshaving a closely-fitted connection to the other end of said mountingbar, bearing means for slidably supporting said drawbars substantiallyin parallelism, means for resiliently biasing each of said drawbars in adirection away from said mounting bar, means operatively engaging saidmounting bar and cooperating with said drawbars for reciprocating saidmounting bar towards and away from said flexing bar member, a pluralityof means for counting the reciprocations of said mounting bar eachcomprising an electric counter, and means for energizing each electriccounter in accordance with each reciprocation of said mounting bar, aplurality of electrically conductive weights each adapted to be attachedto a specimen filament which is secured to said mounting bar and whichextends over said flexing bar, means comprising an electrical controlcircuit connected to each electric counter for deenergizing eachrespective counter on breakage of its respective specimen filamentsecured to said mounting bar, each of said electrical control circuitsincluding a circuit breaker connected to its respective counter forcontrolling the energization thereof, means including a low contactpressure switch for supplying a biasing signal for energizing saidcircuit breaker to actuate it to open-circuit position responsive tobreakage of its said respective specimen filament whereby said counteris deenergized, said low contact pressure switch comprising a cup memberof electrically insulating material having a female conical surfacetherein with the base thereof facing upwardly under one of said weightsattached to a specimen filament secured to said mounting bar, said cupmember having a slot therethrough extending diametrically across saidfemale conical surface splitting the same into two parts, anelectrically conductive surface on both parts of said split femaleconical surface insulatedly separated from each other, and meanselectrically connecting said conductive surfaces on said split parts tosaid circuit breaker for supplying said biasing signal theretoresponsive to an electrical connection of said conductive split femaleconical surfaces by said conductive weight.

6. A filament fiexure fatigue tester comprising a flexing member, meansincluding a filament mounting bar having a plurality of longitudinallyspaced upwardly extending pegs for mounting filament holding tabsthereon, said mounting bar having a slot substantially perpendicular tosaid pegs and bifurcating an end thereof, means including a pair ofdrawbars arranged with one end of one of said drawbars extending throughsaid mounting bar slot for supporting said mounting bar and having meanson .the end of said one drawbar for operatively engaging the respectiveadjacent end of said mounting bar and the corresponding end of the otherof said drawbars having a closely fitted connection to the other end ofsaid mounting bar, bearing means for slidably supporting said drawbarssubstantially in parallelism, means for resiliently biasing each of saiddrawbars in a direction away from said mounting bar, means operativelyengaging said mounting bar and cooperating with said drawbars forreciprocating saidmounting bar towards and away from said flexing 'barmember, a plurality of means corresponding to said plurality of filamentmounting pegs for counting the reciprocations of said mounting bar eachcomprising an electric counter and means for periodically energizingeach electric counter in accordance with each reciprocating operation ofsaid mounting bar, a plurality of electrically conductive weights eachadapted to be attached to a specimen filament which is secured to one ofsaid mounting pegs and which extends over said flexing bar, meanscomprising an electrical control circuit connected to each electriccounter for deenergizing each respective counter on breakage of itsrespective specimen filament secured to its respective mounting peg,each of said electrical control circuits including a circuit breakerconnected to said counter for controlling the energization thereof,means including a low contact pressure switch for supplying a biasingsignal for energizing said circuit breaker responsive to breakage of itssaid respective specimen filament whereby said circuit breaker isactuated to open-circuit position and said counter is deenergized, saidlow contact pressure switch comprising a cup member of electricallyinsulating material having a female conical surface therein with thebase thereof facing upwardly under one of said weigh-ts attached to aspecimen filament secured to said peg, said cup member having a slottherethrough extending diametrically across said female conical surfacesplitting the same into two parts, an electrically conductive surface onboth parts of said split female conical surface insulatedly separatedfrom each other, and means electrically connecting said conductivesurfaces on said split parts to said circuit breaker for supplying saidbiasing signal thereto responsive to an electrical connection of saidconductive split female conical surfaces by said conductive weight.

7. A filament fiexure fatigue tester comprising a flexing bar memberhaving a curved surface forming a flexing edge, means including afilament mounting bar having a plurality of longitudinally spacedupwardly extending pegs for mounting filament holding tabs thereon, saidmounting bar having a slot therein, means including a drawbar arrangedwith one end loosely extending through said mounting bar slot and havingmeans on the end thereof for operatively engaging said mounting bar,bearing means for slidably supporting said drawbar, means forresiliently biasing said draw-bar in a direction away from said mountingbar, means operatively engaging said mounting bar 'and cooperating withsaid drawbar for reciprocating said mounting bar towards and away fromsaid flexing edge, a plurality of means corresponding to said pluralityof filament mounting pegs for counting the reciprocations of saidmounting bar each comprising an electric counter and means forperiodically energizing each electric counter in accordance with eachreciprocation of said mounting bar, a plurality of electricallyconductive weights each of a predetermined size adapted to be attachedto a specimen filament secured to one of said mounting pegs andextending over said flexing edge, means comprising an electrical controlcircuit connected to each electric counter for deenergizing eachrespective counter on breakage of the specimen filament secured to itsrespective mounting peg, each of said electrical control circuitsincluding a circuit breaker connected to said counter for controllingthe energization thereof, means including a low contact pressure switchfor supplying a biasing signal for energizing said circuit breaker foractuation thereof to open circuit position responsive to breakage of itssaid respective specimen filament whereby said counter is deenergized,said low contact pressure switch comprising a cup member of electricallyinsulating material having a female conical surface therein with thebase thereof facing upwardly substantially in longitudinal alignmentwith its respective mounting peg and adapted to be directly under one ofsaid weights attached to a specimen filament secured to said peg, saidcup member having a slot therethrough extending diametrically acrosssaid female conical surface splitting the same into two par-ts, an-electrically conductive surface on both parts of said split femaleconical surface insulatedly separated from each other,

and means electrically connecting said conductive surfaces on said splitparts to said circuit breaker for supplying said biasing signal theretoresponsive to an elec- 12 trical connection of said conductive splitfemale conical surfaces by said conductive weight.

8. A filament fiexure fatigue tester comprising a fiexing membercomprising a small substantially round cylindrical element forming acurved flexing edge with a diameter of between .5 and 5 filamentdiameters, means rigidly mounting said small cylindrical element memberfor maintaining a fixed flexing edge, means including a filamentmounting bar having a plurality of upwardly extending pegs spacedlongitudinally thereof for mounting filament holding tabs thereon, meansincluding a pair of drawbars arranged with one end of each operativelyengaging a separate end of said mounting bar for supporting saidmounting bar, bearing means for slidably supporting said drawbarssubstantially in parallelism, means including a compression spring forresiliently biasing each of said drawbars in a direction away from saidmounting bar and biasing said end means thereon into firm engagementwith said mounting bar, means including an eccentric roller drive memberoperatively engaging said mounting bar and cooperating with saiddrawbars for sinusoidally reciprocating said mounting bar towards andaway from said flexing edge, a plurality of means corresponding to saidplurality of filament mounting pegs for counting the reciprocations ofsaid mounting bar each comprising an electric counter and a cam operatedrelay for periodically energizing each electric counter in accordancewith each reciprocation of said mounting bar, a plurality ofelectrically conductive weights each of a predetermined size adapted tobe attached to a specimen filament secured to one of said mounting pegsand extending over said fiexing edge, means comprising an electricalcontrol circuit connected to each electric counter for deenergizing eachrespective counter on breakage of the specimen flament secured to itsrespective mounting peg, each of said electrical control circuitsincluding a circuit breaker connected to said counter for controllingthe energization thereof, a signal amplifying circuit for energizingsaid circuit breaker to open circuit position whereby said counter isdeenergized, means including a low contact pressure switch for supplyinga biasing signal to said amplifying circuit responsive to breakage ofits said respective specimen filament, said low contact pressure switchcomprising a pair of electrically conductive elements insulated fromeach other and adaptable to be electrically connected by said weight onbreakage of the respective specimen filament and being connected in saidamplifying circuit for supplying said biasing signal thereto.

9. A filament fiexure fatigue tester comprising a flexing bar memberhaving a curved surface forming a flexing edge with a diameter ofbetween .5 and 5 filament diameters accurately formed to a uniformlyrounded curvature and size, means including a filament mounting barhaving a plurality of upwardly extending pegs spaced longitudinallythereof for mounting filament holding tabs thereon, means including apair of drawbars arranged with one end of each operatively engaging aseparate end of said mounting bar for supporting said mounting bar,bearing means for slidably supporting said drawbars substantially inparallelism, means including a compression spring for resilientlybiasing each of said drawbars in a direction away from said mounting barand biasing said end means thereon into firm engagement with saidmounting bar, means including an eccentric roller drive memberoperatively engaging said mounting bar and cooperating with saiddrawbars for sinusoidally reciprocating said mounting bar towards andaway from said flexing edge against the resilient pressure of saidsprings, a plurality of means corresponding in number to said pluralityof filament mounting pegs for counting the reciprocations of saidmounting bar each comprising an electric counter and a cam operatedrelay for periodically energizing each electric counter in accordancewith each reciprocation of said mounting bar, means including aplurality of electrically conductive weights each of a predeterminedsize adapted to be attached to a specimen filament secured to one ofsaid mounting pegs and extending over said flexing edge, meanscomprising an electrical control circuit connected to each electriccounter for deenergizing each respective counter on breakage of thespecimen filament secured to its respective mounting peg, each of saidelectrical control circuits including a circuit breaker connected tosaid counter for controlling the energization thereof, a signalamplifying circuit for energizing said circuit breaker to open circuitposition whereby said counter is deenergized, means including a lowcontact pressure switch for supplying a biasing signal to said signalamplifying circuit responsive to breakage of its said respectivespecimen filament, said low contact pressure switch comprising a cupmember of electrically insulating material having a female conicalsurface therein with the base thereof facing upwardly under one of saidweights attached to a specimen filament, said cup member having a slottherethrough extending diametrically across said female conical surfacesplitting the same into two parts, an electrically conductive surfacecomprising a thin coating of conductive paint on both parts of saidsplit female conical surface extending from short of the apex thereof toassure complete insulation between said split parts and over said outerbase and outer side of said cup to points separated by said slot, andmeans electrically connecting said conductive surfaces on said splitparts to said signal amplifying circuit for supplying said biasingsignal thereto responsive to an electrical connection of said conductivesplit female conical surfaces by said conductive weight.

10. A filament flexure fatigue tester including a flexing membercomprising a wire forming a curved flexing edge with a diameter ofbetween .5 and filament diameters, means rigidly mounting said flexingwire member for maintaining a fixed flexing edge, means including afilament mounting member and a drive sinusoidally reciprocating saidmounting member for reciprocating a filament mounted thereon back andforth over said flexing edge,

electrical means for counting the reciprocations of said mountingmember, an electrically conductive weight of predetermined size adaptedto be attached to a specimen filament secured to said mounting memberand extending over said flexing edge, means comprising an electricalcontrol circuit connected to said electrical counting means fordeenergizing said counting meanson breakage of the specimen filamentsecured to said mounting member, said electrical control circuitincluding a circuit breaker connected to said counting means forcontrolling the energization thereof, a signal amplifying circuit forenergizing said circuit breaker to open-circuit position whereby saidcounting means is deenergized, means including a low contact pressureswitch for supplying a biasing signal to said signal amplifying circuitresponsive to breakage of its said specimen filament, said low contactpressure switch comprising a cup member of electrically insulatingmaterial having a female conical surface therein with the base thereoffacing upwardly under said weight attached to a specimen filament, saidcup member having a slot therethrough extending diametrically acrosssaid female conical surface splitting the same into two parts, anelectrically conductive surface on both parts of said split femaleconical surface extending from short of the apex thereof to assurecomplete insulation between said split parts and over said outer baseand outer side of said cup to points separated by said slot, and meanselectrically connecting said conductive surfaces on said split parts tosaid amplifying circuit for supplying said biasing signal theretoresponsive to an electrical connection of said conductive split femaleconical surfaces by said conductive weight on breakage of said specimenfilament.

References Cited in the file of this patent UNITED STATES PATENTS

